I'm only 27, but I blew out my knee a year ago. I tore my meniscus, MCL and ACL. I carried a cane for a few months (after graduating from a wheelchair and crutches) and thought of it as a good defensive tool. I always carried an assisted opening knife, but did not yet have my CCW permit.
Now that I have my CCW permit, I always carry a handgun and I feel that my cane would just slow my draw. If I tweak my knee, which still happens from time to time, I will use the cane for a few days. If I have to have it, I make it a part of my SD plan.
I'm amazed by how many people assume, due to my limp and my age, that I am an Iraq or Afghanistan vet. Especially when I had the cane, people would hold the door and make comments like, "Thanks for your service". It's kind of embarrassing to tell them I'm not a vet... The real story isn't nearly that interesting.